Introduction
Taper Pipe NPTF L3 Plug Gage is used for the inspection of the L-3 length of the engagement for taper and wrench tight. What makes NPTF gages different from NPT gages is that they are considered dry seal pipe threads. They are also called relationship gages which are used for inspecting the taper coupling and wrench engagement of the internal threads or couplings. Taper Pipe NPTF L3 Plug Gage is used in conjunction with NPTF L1 gages hence the name “relationship gage”.
Use
When internal threads are gaged, Taper Pipe NPTF L3 Plug Gage is one of the three main members used where the Taper Pipe NPTF L3 Plug Gage is used to checking the threads that will be engaged at the stage of wrench tightening. Since the gages are different in terms of dimension, it is vital that they must not be interchanged from one another.
NPTF vs. NPT
The primary difference is in the name, then there is a major difference of no sticking medium used like Teflon tape or pipe dope between the two threads in NPTF. NPTF gages are designed to bear a high critical crest tolerance which is why they are commonly inspected with a smooth 6 step plug or ring gage. The gage is used in conjunction with the NPT L1 gage that helps in establishing the tolerance of the product in question (whether the tolerance is min, nominal, or max.)
The L3 in the name of Taper Pipe NPTF L3 Plug Gage refers to the need for a secondary inspection which may be required on the said threads for which the L3 plug is used. Do note that the plug is used for the inspection of the internal threads whereas ring gages are used for the inspection of external threads. Both L1 and L3 plugs are used on threads that are not plated. As such, it is imperative that the gage must not move 0.5 turns (+/-) from the position of the L1 gage. Gages that are plated have a different tolerance.
Precautions
It is vital that the Taper Pipe NPTF L3 Plug Gage must be treated with diligence as a precision tool as any type of mishandling or misuse, or forced use can cause unwanted deformities or nicks. This can compromise the integrity of the gage hence the measurements. Also, the gage must never be forced into a part that is under check. Moreover, keep the gage separate and never cram it with other tools as it may damage the threads of the gage.
When you are done with the use of the tool, it is advised that you should oil or grease the tool to protect it from rust. Finally, if Taper Pipe NPTF L3 Plug Gage is to be shipped over long distances, store it in a separate container with insulation to prevent it from being damaged.
Conclusion
Taper Pipe NPTF L3 Plug Gage is a part of class 2 gages that are used specifically for measuring the crest and threads. The plugs themselves can only be checked with a master thread plug which is why it is advised to keep a spare. Production units with regular and excessive use of Taper Pipe NPTF L3 Plug Gage are advised to have several spares at hand along with a master thread plug to regularly check on wear and tear of their Taper Pipe NPTF L3 Plug Gage.
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